INA250-Q1: 3 parallel

Hello Doi-san,

In general, when you add more devices together the errors combine in a root-sum-of-the-squares fashion, but looking at TIDUA90, it seems that 3 parallel devices should have similar accuracy to 2 parallel devices. Is there a specific reason why your customer is using 3 parallel INA250’s instead of one single device such as the INA210 and a smaller shunt resistor? Will these be connected in parallel from the same source or will they be summed from 3 different sources, as in a 3-phase, low-side measurement?

I am not sure what you mean by Secondary side transmission. Could you please elaborate on that for me? If you have a schematic for me to look at, that would be very helpful.

Hello Mitch-san,

Limited parts can be used in CAR.

They do not want to increase the type of parts.

They already evaluating INA250A1QPWRQ1 and AMC1301-Q1.

Do you know Isolated DCDC?

I think they want to measure primary side big current and send the result to secondary side MCU.

Between primary side and secondary side, isolation is required such as opto-coupler.

So I think AMC1301-Q1 is much better because no need opto-coupler.

Of course they do not want to use newly high precision low resister,

I recomend 3 pieces of INA250A1QPWRQ1 for higher level current.

Thanks,

Hello Doi-san

Where is your boundary for isolation? Is it between the INA and a microcontroller or is it between the INA amplifier and the shunt? What are you isolating it from?

To answer one of your earlier questions about future releases for the INA250-Q1, we are looking at lower ohmic value options but these are still in the early development stages at the moment.

Hello Mitch-san,

I'ts customer secret issue.

Dan Harmon-san visited Japan customer on Oct.21th 2016.

I think he has Block Dia.

Thank you,

Hello Doi-san,

I have received the block diagrams from Dan Harmon, and I'm not quite sure which location you are referencing, as the INA250-Q1 is used in multiple places. If using the INA250-Q1 with 3 in parallel, would you need isolation on each of them, or just one of them? What current level are you dealing with?

Mitch-san,

left side  INA250  drive Opto coupler (Isolation) 

Opto coupler -> transistor -> Micro

EV power level is growing every month.

I think No EV car in Dallas, but in now China major city, half of cars sale are EV or PHV, 

40A, 50A, 60A,....

Hello Doi-san,

Each INA250-Q1 device can only handle a maximum of 15A each, so with 3 in parallel you would be limited to 45A. If you needed 60A you would have to use 4 devices in parallel. When putting the devices in parallel, make sure that the supply voltage can handle the total output for the devices. For example, if you use the A1 version of the INA250-Q1 with a gain of 200mV/A, then with 15A you would have a 3V output going into the REF pin of the second device which would then have a 6V output going into the third device and so on. Therefore, with 4 devices you would need a supply greater than 12V. Also, it is important to note that the REF pin is limited to 18V, so if you used the A2 gain version with 500mV/A then the output of the first device would be 7.5V making the output of the third device 22.5V which is too large to go into a fourth device. So what this means to you is that if you want to do more than 3 devices in parallel then you are limited to the A1 gain version.

Although this solution looks doable, it may be better to qualify a different device such as the INA214C-Q1. With this device if you used a 500uOhm shunt and a gain of 100V/V then at 60A you would only have a 3V output.

I am reaching out to the precision amplifiers team to see if the AMC1301-Q1 also provides a workable solution.